In one data input device for electronic devices having a display device such as liquid crystal device (LCD) and CRT, a data input device is disposed on a screen of the display device and is touched with a finger or the like while seeing through the screen (hereinafter, the data input device is referred to as touch panel, see JP-A-2005-317041 for example). When a character, number, and other symbol (which may include pictorial symbols called as icon configured by figures, images, and the like, and each of which may be configured by a plurality of symbols) displayed on a screen is touched, the touch panel generates and outputs information corresponding to a position of an intended character, number, or symbol.
For example, a touch panel type display has been widely used in an electronic device not only such as an ATM of banks and a car navigator but also in a small-sized electronic device such as portable information terminal and electronic dictionary.
Meanwhile, various proposals for implementing data input devices, in the touch panels is used without the display devices such as LCD and CRT, have been proposed. For example, the applicant have proposed a keyboard device, in which a display function is not required, having an input operation surface, which is provided at the top surface and has a flat surface as a touch panel type display (see JP-A-2009-253938).
A data input device using the touch panel is widely used in not only devices such as keyboard devices having various operation sections but also, for example, an operation section for a home appliance, a residential device, and the like, instead of a conventional data input device having a keycap (see JP-A-2007-208682)
The keyboard device disclosed in JP-A-2009-253938 and the data input device of the operation section of the home appliance, the residential device and the like use a capacitive touch sensor for implementing a flat input operation section having highly sensitive input detection. Since the flat input operation surface is flat, a cleaning is easy and a contamination is difficult to be fixed. Therefore, the appearance is improved and a clean condition can be maintained. That is, the keyboard device and the data input device achieve the functionality and aesthetics at high level.
Meanwhile, the capacitive sensor determines whether the operation is performed, based on a change of a detected capacitance. Therefore, the capacitive sensor has a unique problem, which has not appeared in the conventional data input devices detecting an input by receiving a displacement due to a touch of a keycap.
For example, during manufacturing of touch sensors, the characteristics of each of the touch sensors, a variation in detection sensibilities due to component accuracy and the like may cause a variation in detection amount (detection value regarding capacitance) in each of the touch sensors for each key, as shown in FIG. 4. In an example of FIG. 4, a detection amount of the key C of the touch sensor is the largest, a detection amount of the key B of the touch sensor is the smallest, and a detection amount of the key A of the touch sensor is an intermediate value. In this case, if detection sensitivities of the touch sensors for determining whether the input operation is performed are defined by a uniform threshold, the input operation of the key B of the touch sensor cannot be detected. In view of the above, adjustments of the thresholds of the detection sensitivities of touch sensors are required before shipment of the data input device.
Even after shipment of the data input device, a variation in the detection amount among touch panels as shown in FIG. 4 may be caused by habits of operators and so on. Also, a similar variation may be caused by deformation of components due to a change of an environment in which the data input device is placed a change of a temperature or a humidity, for example. Therefore, if it is possible that the determined detection sensitivity of the touch sensors set before shipment (default state) is changed in accordance to a change of sensitivity caused by preferences of the operators and a change of the environment after the shipment, it is possible to improve the usability of the data input device significantly. On the other hand, if a change of detection sensitivity of the touch panels is allowed unlimitedly, it is feared that a change of capacitance with respect to input operation may be insufficient to receive the input operation, and thus intended operation cannot be performed.
The present disclosure was made in consideration of the above, and the present disclosure is provided to change appropriately the detection sensibility of the touch sensor in the data input device for an electronic device using capacitive touch sensors, without damaging the reliability.